Early methods of lancing included piercing or slicing the skin with a needle or razor. Current methods utilize lancing devices that contain a multitude of spring, cam and mass actuators to drive the lancet. These include cantilever springs, diaphragms, coil springs, as well as gravity plumbs used to drive the lancet. Typically, the device is pre-cocked or the user cocks the device. The device is held against the skin and mechanically triggers the ballistic launch of the lancet. The forward movement and depth of skin penetration of the lancet is determined by a mechanical stop and/or dampening, as well as a spring or cam which retract the lancet.
Variations in skin thickness and hydration can yield different results from different users of the lancing device. Current devices rely on adjustable mechanical stops or damping to control the lancet's depth of penetration and compensate for skin thickness and hydration. Such mechanical stops do not regulate the acceleration in order to control the velocity of the lancet as it is protracted and retracted. Conversely, cams offer rough control of lancet velocity in and out of the skin, but do not allow for compensation for skin thickness and hydration. Hence, not-all lancing events are successful in generating a blood sample sufficient for the desired analytical test.
Success rate means the probability of producing a blood sample with one lancing action which is sufficient in volume to perform the desired analytical test. The blood droplet produced by the action must reach the surface of the skin to be viable for testing. In some instances, blood will flow from the cut blood vessels but is trapped below the surface of the skin, forming a hematoma. In other instances, a subcutaneous wound is created, but no external blood is obtained. The success rate of obtaining an acceptable blood sample with industry standard lancets available on the market today is 75% to 80%; meaning that up to one in five lancing operations will yield insufficient blood or no blood. For patients required to self test five to six times daily, this inability to obtain a blood droplet every time the finger is lanced translates into needlessly repeating a painful protocol.